Anatomy & Physiology
Digestion is the process by which food is broken down into smaller pieces so that the body can use them to build and nourish cells and to provide energy. Digestion involves the mixing of food, its movement through the digestive tract (also known as the alimentary canal), and the chemical breakdown of larger molecules into smaller molecules. Every piece of food we eat has to be broken down into smaller nutrients that the body can absorb, which is why it takes hours to fully digest food.
The digestive system is made up of the digestive tract. This consists of a long tube of organs that runs from the mouth to the anus and includes the esophagus, stomach, small intestine, and large intestine, together with the liver , gall bladder , and pancreas, which produce important secretions for digestion that drain into the small intestine. The digestive tract in an adult is about 30 feet long.
Mouth and Salivary Glands Digestion - begins in the mouth, where chemical and mechanical digestion occurs. Saliva or spit, produced by the salivary glands (located under the tongue and near the lower jaw), is released into the mouth. Saliva begins to break down the food, moistening it and making it easier to swallow. A digestive enzyme(called amylase) in the saliva begins to break down the carbohydrates(starches and sugars). One of the most important functions of the mouth is chewing. Chewing allows food to be mashed into a soft mass that is easier to swallow and digest later. Esophagus - Once food is swallowed, it enters the esophagus, a muscular tube that is about10 inches long. The esophagus is located between the throat and the stomach. Muscular wavelike contractions known as peristalsis push the food down through the esophagus to the stomach. A muscular ring (called the cardiac sphincter) at the end of the esophagus allows food to enter the stomach, and, then, it squeezes shut to prevent food and fluid from going back up the esophagus. Stomach - a...
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